Just how plain are plain tobacco packs: re-analysis of a systematic review using multilevel meta-analysis suggests lessons about the comparative benefits of synthesis methods

Abstract

BackgroundComparisons between narrative synthesis and meta-analysis as synthesis methods in systematic reviews are uncommon within the same systematic review. We re-analysed a systematic review on the effects of plain packaging of tobacco on attractiveness. We sought to compare different synthesis approaches within the same systematic review and shed light on the comparative benefits of each approach.MethodsIn our re-analysis, we included results relating to attractiveness in included reports. We extracted findings from studies and converted all estimates of differences in attractiveness to Cohen’s d. We used multilevel meta-analysis to account for clustering of effect sizes within studies.ResultsOf the 19 studies reporting results on attractiveness, seven studies that included between-subjects analyses could be included in the meta-analysis. Plain packs were less attractive than branded packs (d = − 0.59, 95% CI [− 0.71, − 0.47]), with negligible but uncertain between-studies heterogeneity (I2 = 0%, 95% CI [0.00, 70.81]) and high within-study heterogeneity (I2 = 92.6%, 95% CI [91.04, 93.90]).ConclusionsThe meta-analysis found, similar to the narrative synthesis, that respondents typically rated plain packaging as less attractive than alternative (e.g. branded) tobacco packs. However, there were several trade-offs between analysis methods in the types and bodies of evidence each one contained and in the difference between partial precision and breadth of conclusions. Analysis methods were different in respect of the role of judgement and contextual variation and in terms of estimation and unexpected effect modification. In addition, we noted that analysis methods were different in how they accounted for heterogeneity and consistency.Electronic supplementary materialThe online version of this article (10.1186/s13643-018-0821-7) contains supplementary material, which is available to authorized users.

Synthesis without meta-analysis (SWiM) in systematic reviews: reporting guideline

“…Avoidance of the term “narrative synthesis” in SWiM is a deliberate move to promote clarity in the methods used in reviews in which the synthesis does not rely on meta-analysis. The use of narrative is ubiquitous across all research and can serve a valuable purpose in the development of a coherent story from diverse data 3334. However, within the field of evidence synthesis, narrative approaches to synthesis of quantitative effect estimates are characterised by a lack of transparency, making assessment of the validity of their findings difficult 7.…”

Will plain packaging of cigarettes achieve the expected? Perceptions among medical students

“…Studies mainly indicate that plain packaging increases the salience of health warnings and pictorials. The pictorials on plain packages are noticed more easily, recalled better and have a stronger impact 7,10,15,17,19,20,[28][29][30]36,37 . Our results also indicate that the effects of the pictorials are more profound in the plain packs compared to the branded ones.…”

An overview of methodological approaches in systematic reviews

“…Narrative and quantitative syntheses are the two most commonly used approaches for synthesizing data in evidence synthesis 5 . There are some published studies on the proposed indications and implications of these two approaches 30,31 . These studies found that both data synthesis methods produced comparable results and have their own advantages, suggesting that the choice of the method must be based on the purpose of the review 31 .…”

“…5 There are some published studies on the proposed indications and implications of these two approaches. 30,31 These studies found that both data synthesis methods produced comparable results and have their own advantages, suggesting that the choice of the method must be based on the purpose of the review. 31 With increasing number of "expedited" SR approaches (so called "rapid reviews") avoiding MA, 10,11 further research studies are warranted in this area to determine the impact of the type of data synthesis on the results of the SR.…”